Automatic burner



Nov. 5, 1957 I l. N. VANT 2,812,017

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AUTOMATIC BURNER Filed Feb. 24, 1953 5 Sheets-Sheet 2 INVENTOR. 54002!AA Mwvr Nov. 5, 1957 l. N. VANT AUTOMATIC BURNER 5 Sheets-Sheet 5 FiledFeb. 24, 1953 m a/i/wm (54002: M l/wr 3) \vll T r 1 1 I I IL U.

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AUTOMATIC BURNER Filed Feb. 24, 1953 5 Sheets-Sheet 4 nvvavrap 6,4002:/V. I m r Nov. 5, 1957 1. N. VANT 2,812,017

AUTOMATIC BURNER Filed Feb. 24, 1953 5 Sheets-Sheet 5 Arrow i) UnitedStates Patent AUTOMATIC BURNER Isadore N. Vant, Palo Alto, Calif.

Application February 24, 1953, Serial No. 338,430

2 Claims. (Cl. 158-81) This invention relates to a burner. Moreparticularly it relates to a burner system which employs gasoline orother volatile liquid fuel and which is adapted to operateautomatically.

This application is a continuation-in-part of my copending applicationSerial No. 97,560, entitled Fire Unit, filed June 7, 1949, nowabandoned, and of my co-pending application Serial No. 101,43 6,entitled Combined Heater and Prime Mover, filed June 25, 1949, nowabandoned.

In burners intended to operate on a volatile liquid fuel such asgasoline, it is necessary to vaporize the fuel before introducing itinto the burner. Also, where the fuel is leaded gasoline and the burneris employed in a confined space, as in any army field kitchen, or in acamp stove located in a tent, it is advisable to decompose the leadcompounds and to filter out the products of decomposition before thegasoline reaches the burner. By lead compounds are meant compounds suchas tetraethyl lead which is generally used to improve the antiknockproperties of gasoline.

It is an object of the present invention to provide improved means ofvaporizing fuel and of removing lead from leaded fuels.

In burners of the character described, it is also desirable to provide ameans for starting the burner which is easy and dependable in operation.This is a problem of some considerable difiiculty where a liquid fuelmust first be vaporized, and it is particularly difficult where thevapor must be heated sufiiciently to decompose lead compounds.

It is a further object of the present invention to provide startingmeans for a gasoline burner or the like which is easily operated, whichis dependable and which will rapidly heat a fuel vaporizer or generatorsufficiently to vaporize fuel and, if necessary, to also decompose leadcompounds contained in the fuel.

It is another object of the invention to provide a starting or primingmeans for a gasoline burner which is automatic in its operation and willpressurize the system and heat a fuel vaporizer or generator tooperating temperature.

A further object is to provide improved means of maintaining the fueltank of a gasoline burner under constant pressure and of automaticallylimiting the fuel pressure so as not to exceed a predetermined, safevalue.

Yet another object is to provide a means for automatically stopping thefeed of liquid fuel to the burner when the pressure in the fuel tankexceeds a certain predetermined value.

A further object is to provide a means of avoiding or minimizing thepulsation of a gasoline burner, especially when the burner is operatingat a low pressure.

These and other objects of the invention will be apparent from theensuing description and the appended claims.

Certain forms of the invention are illustrated by way of example in theaccompanying drawings, in which,

Figure 1 is a diagrammatic view of a complete burner system embodyingthe present invention.

Figure 2 is a view similar to that of Figure 1, but showing a differenttype of filter.

Figure 3 is a top plan view of a burner assembly embody ing the presentinvention.

Figure 4 is a side elevation of the burner assembly of Figure 3.

Figure 5 is a perspective view of a portion of the burner assembly ofFigure 3, certain parts being broken away for clarity.

Figure 6 is a view in section taken along the line 6-6 of Figure 4,showing the intake of the burner.

Figure 7 is a section taken along the line 7-7 of Figure 3 showing theauxiliary assembly.

Figure 8 is a section taken along the line 88 of Figure 4, showing oneof the automatic pressure regulating valves in detail.

Figure 9 is a section taken along the line 9-9 of Figure 3 showing themain burner and the auxiliary assembly.

The general construction and operation of the burner system of thepresent invention will be described first with reference to Figure 1,then, in more detail, with reference to Figures 3 to 9.

Referring now to Figure 1, the burner system is generally designated as10 and it comprises themain burner 11, a fuel tank 12, a combinedvaporizer or generator and filter 13, an auxiliary burner 14, a starterburner 15, a main burner valve 16 and a starter Valve 17.

To start and prime the burner system, the main burner valve 16 is closedand the starter valve 17 is opened. Both the valves 16 and 17 aremanually operated valves. When the starting valve 17 is opened volatileliquid fuel such as gasoline, shown at 18 in the fuel tank 12, flows bygravity through a line 19 which has a normally open, automatic, pressureregulating valve 20 and is also connected to a pressure gauge 25. Liquidfuel continues to flow by gravity through the line 19 into a straightlength of pipe 26 and issues from the end 27 which is formed with arestricted orifice or nozzle. The fuel wets the wick 29 contained in aperforated trough 29. When this occurs, the gasoline in the wick islighted with a match or other flame. The resulting flame serves to heatthe extreme left hand end of the pipe 26 and thereby quickly vaporizesthe gasoline in the pipe. The nozzle end 27 of the pipe 26 and theadjacent end 30 of the starter burner 15 form a venturi which mixes thegasoline vapor formed in the pipe 26 and issuing from the nozzle endthereof, with air. The resulting fuel vapor-air mixture passes into thestarter burner 15 and emerges from slots 32 formed therein. Due toproximity of the starter burner 15 to the wick 28, the starter burner isimmediately ignited by the Wick. The starter burner continues to burn,thereby heating both a pipe 33 and the vaporizer-filter 13. The pipe 33is connected at one end to the line 19 and at its other end it isconnected to the top of the fuel tank 12 so as to communicate with thevapor space 18a in the tank.

Heat from the starter burner 15 accomplishes two functions; as follows:Gasoline flows by gravity into the pipe 33. This gasoline is heated andvaporized and the fuel vapor passes through the pipe 33 to the vaporspace 18a in the fuel tank 12. By this means pressure is built up in thefuel tank 12 and in the system as a whole. Meanwhile, heat from thestarter burner also heats the vaporizer-filter 13, which may contain afilter medium such as shown at 34. Operation of the starter burner iscontinued until a predetermined pressure is registered on the gauge 25,e. g., a pressure of 30 p. s. i. When the system has been thuspressurized by means of the starter burner, there exists a sufficientpressure, and the vaporizer-filter 13 is sufiiciently hot, for operationof the main burner. The main burner valve 16 is then opened. Liquid fuelwill then pass through a line 35 containing a normally open, automatic,pressure regulating valve to the vaporizerfilter 13. Thevaporizer-filter is sufficiently hot to vaporize the liquid fuel and todecompose lead compounds, which are filtered out by the filter medium34. The filtered fuel vapor then passes through a line 41 and the mainburner valve 16 to the burner intake 42, wherein it is mixed with airand introduced into the main burner 11. vapor-air mixture issuing fromthe burner 11 is then ignited, and the starter valve 17 is closed toextinguish the starter burner 15.

When the starter valve 17 is closed, the starter burner ceases to supplyhat to the vaporizer-filter 13 and to the pipe 33, but this function istaken over by the auxiliary burner 14, which is supplied with fuel-airmixture by the main burner 11 through a passage 43.

In the operation of a gasoline burner it is important to maintain thefuel supply in the fuel tank under sufficient pressure for continued,efficient operation of the burner. It is, however, important to preventthe pressure in the fuel tank from becoming excessive. In some priorburner systems the pressure control is such that, as the fuel pressureincreases, more fuel is fed to the burner. This makes the flame hotter,which in turn increases the pressure and supplies even more fuel to theburner. As a result, hazardous explosions are possible and have in factoccurred. On the other hand, it is desirable to avoid a control systemwhich cuts off fuel supply to the burner entirely when the fuel pressureexceeds a predetermined value, because complete extinction of the burneris troublesome.

In accordance with the present invention a safe, dependable automaticpressure control is provided which is efiective to control the fuelpressure and to prevent it from exceeding a safe value, without causingextinction of the burner. The automatic, pressure regulating valve 20 issuch that when the pressure in the fuel tank 12, ex-

ceeds a predetermined value, e. g., p. s. i., the valve will closeautomatically, thereby interrupting the supply of liquid fuel to thepipe 33. This will interrupt the supply of pressurized fuel vapor to thefuel tank 12. Nevertheless, the burnerll will continue to operatebecause it is supplied with fuel through the line and the otherautomatic, pressure regulating valve 40. It will thus be apparent that,under most operating conditions, the pressure in fuel tank 12 cannotexceed a predetermined value, but that this control does not interruptoperation of the burner.

The valve provides yet another automatic safety feature, as follows: Aburner system such as that illustrated in Figure l is frequentlyenclosed in a small space, Y e. g., in a cook stove such as employed inarmy camps.

Such compactness and shielding will necessarily confine the heat fromthe burner and will heat the fuel tank. Under adverse conditions, suchas long continued operation of a burner in a warm climate or in a heatedroom, the fuel tank may overheat and raise the fuel pressure to adangerous level.

To overcome this hazard I provide the automatic, pressure regulatingvalve 40 in the line 35. The valve 40 may be the same as the valve 20.For example, the valve 40 may be set to close at 40 p. s. i. and whenthe pressure on the left hand side thereof as viewed in Figure l, i. e.,on the inlet side of the valve, reaches 40 p. s. i. Thus, should thepressure in the fuel tank 12 become excessive because of the ambienttemperature, the valve 40 will automatically close thereby shutting offthe supply of liquid fuel to the burner 11. Nevertheless, the burner 11will not be extinguished because of the following feature:

A pipe is provided which is connected at one end to the line 35 andwhich extends through the wall of tank 12 and is open at its other endto the vapor space 18a in the fuel tank 12. It will be noted that thepipe 45 connects with the line 35 to the right of the automatic pressureregulating valve 40. The purpose of the pipe 45 is as follows: When thevalve 40closes in response to excessive pressure in the fuel tank12,.the supply of liquid The fuel 4 fuel to the vaporizer-filter 13 is,of course, stopped immediately. However, fuel vapor in the space 18awill pass through the pipe 45 into the line 35, thence through thevaporizer-filter 13 to the burner 11 to support combustion. The excesspressure will be relieved very rapidly, the valve 40 will open again andliquid fuel will be supplied to the vaporizer-filter 13, withoutextinction of the burner 11.

Referring now to Figures 3 to 9, the burner system 10 is shown as beinga compact unit mounted on a base or frame which is slidable into and outof a cookstove or the like. In Figures 3 to 9, elements similar toelements illustrated in Figure l are similarly numbered. As is shownmost clearly in Figure 4, the fuel tank 12 is mounted on a sheet metalcradle 51 and is shielded by a sheet metal shield 52 from the burner 11.As shown in Figures 3 and 4 and also in Figure 9, the burner 11comprises an upright expansion chamber 53 and a burner tip 54 havingradial arms 55 formed with slots 56 for escape of fuel-air mixture. Theburner 11 also has a central plate 57 and a bolt 58 to clamp the partstogether. The burner 11 may be of a conventional construction withsuitable modifications as will appear hereinafter.

As shown in Figures 7 and 9, an auxiliary assembly 59 is mounted on oradjacent to the expansion chamber 53 of the main burner 11. Thisauxiliary assembly comprises the above-mentioned starter burner 15, thepipe 33, the auxiliary burner 14, the vaporizer-filter 13 and the intake42 of the main burner 11. This auxiliary equipment is very compactlyarranged.

Referring now to Figures 4 and 5, the ignition assembly, which isgenerally designated as 65, comprises the abovementioned pipe 26 whichis connected at its inlet end to the line 19 and is provided with aneedle valve 17 which is operable by means of a stem 66 and a knob 67.The pipe 26 is supported by spaced, upright brackets 68 which are fixedto a box 69 which, in turn, is fixed to the frame 50. Forwardly, or tothe left as viewed in Figures 4 and 5, the pipe 26 overlies the trough29 containing the wick 28. The starter burner 15 is also fixed to thebox 69 and, as shown in Figure 7, it is formed with bottom openings 70communicating the starter burner with the interior of the box. As shownin Figure 5, the box 69 is formed with a series of holes 71 which extendtransversely from the starter burner to the vicinity of the pipe 26,thence longitudinally beneath and in registry with the pipe 26.

As described above, the burner system is started by opening the startingvalve 17 to allow liquid gasoline to issue from the nozzle end 27 of thepipe 26 and to wet the wick 28, then lighting the wick. The resultingflame heats the overlying end of the pipe 26 and vaporizes gasolinetherein. Gasoline vapor mixes with air in the venturi formed by thejuxtaposed ends 27 and 30 of pipes 26 and 15, and the resulting gasolinevapor-air mixture passes into the starter burner 15. From an inspectionof Figures 5 and 7, it will be apparent that a portion of the fuel-airmixture supplied to the starter burner 15 will find its way into theinterior of the box 69 through the openings 70. This fuel-air mixturewill issue from the holes 71 formed in the box 69. By reason of theclose spacing and arrangement of the holes 71, the fuel-air mixtureissuing from the holes adjacent the starter burner 15 will ignite andthe flame will travel along the rows of holes 71, thereby igniting thefuel-air ixture issuing from the holes 71 in registry with the pipe 26.By this means an adequate flame is supplied for vaporizing gasoline inthe pipe 26, without the necessity of relying upon the wick 28. Also,the fuel-air mixture issuing from the slots 32 in the starter burner 15will ignite, thus initiating operation of the starter burner.

As described above, operation of the starter burner is continued until apredetermined pressure is registered on the gauge 25. At such time themain burner valve 16 will be opened to admit fuel vapor to the intake42. The

main burner 11 is then ignited and the starter valve 17 is closed, thusterminating operation of the starter burner 15.

Referring now to Figures 5 and 6, the intake 42 of the burner 11 isshown in detail. It comprises an angular pipe 72 having an air intakebranch 73. The main burner valve 16 is a needle valve which is operatedby a stem 74 and a knob 75. The valve 16 terminates in a nozzle orrestricted orifice 76. An air control shutter 77 is provided which islocated at the outer end of the branch 73. It comprises a plate 78 fixedto the branch 73 by means of a screw 79. By adjustment of the screw 79the spacing of the plate 78 can be controlled to admit more or less airas desired.

Referring now to Figure 8, the valve 40 is there shown in detail. Itwill be understood that the valve 20 may be identical in structure. Thevalve 40 comprises a body portion 80 having passages 81 and 82 formedtherein which are interconnected by a passage 83 which terminates in avalve seat 84. The valve proper, shown at 85, is urged upwardly towardthe valve seat by a light expansion spring 86 and it is urgeddownwardly, away from the valve seat, by a much stronger expansionspring 87 which bears against a flexible diaphragm 88 which has agrommet hearing against a rod 89 which is fixed to the valve 85. Thevalve 85 is normally open because of the greater strength of this spring87, but it will be apparent that if a sutficient pressure iscommunicated to the chamber 90 beneath the diaphragm 88 through thepassage 81 to overcome the force of the spring 87, the valve 85 will bemoved to closed position and will remain closed until the pressure inpassage 81 diminishes to a predetermined value. This predeterminedpressure is determined by adjustment of a screw 91 and by the strengthof the spring 87.

Referring now to Figures 3 and 4, a vacuum release valve 92 is thereshown which is connected to the fuel tank 12 and is operated by a rod93. The purpose of this valve is as follows: When the main burner 11 isextinguished and the fuel in tank 12 cools, vapor in the tank 12 willcondense and create a vacuum. If this vacuum persists, difficulty willbe encountered in obtaining gravity flow of fuel when the burner isstarted again. The orifice in pipe 26 is too small to admit air todisplace fuel flowing by gravity from the fuel tank and to relieve thevacuum in the fuel tank. This difiiculty is obviated merely bymanipulating the rod 93 to open the valve 92, allowing air to enter thefuel tank to relieve the vacuum, and then closing the valve 92. The samedifiiculty (no gravity flow of fuel) may exist when the tank 12 isfilled completely with fuel, and the same manipulation relieves thisdifficulty.

Referring now to Figure 2, a burner system is there shown which is thesame as the burner system shown in Figure 1 with the exception of thefilter employed to filter decomposed lead compounds from the fuel vapor.Parts in Figure 2 which are similar to parts in Figure l are similarlynumbered.

The vaporizer 13a may be of the same construction as thevaporizer-filter 13 in Figure 1 except that it does not function as afilter and therefore requires no filtering medium. The vaporizer 13a ispreferably empty and free of any obstruction which would cause apressure drop. Hot fuel vapor containing decomposed lead compounds isconducted through a line 95 to a filter 96 which is disposed within thefuel tank 12. The filter 96 comprises an outer casing or tube 97 whichis disposed within the fuel tank 12 and is immersed in the liquid fuelcontained in the tank. The right hand end of the outer casing 97, asviewed in Figure 2, is closed as shown at 98 and the other, or left handend protrudes through the oppositewall of the tank and is closed bymeans of a fitting 99. An inner tube 100 is disposed within the outertube97 and is spaced therefrom to provide an annular space 101. Theinner or right hand end of the inner tube 100, as viewed in Figure 2, isclosed as shown at 102 and the outer or left hand end extendsthrough'the fitting 9.9.and is provided with a fitting 103. The interiorof the inner tube 100 is filled with a suitable filter medium,preferably glass balls as shown at 104, which are preferably about fourto six millimeters in diameter. Alternatively ceramic material, pebbles,steel balls and other similar materials may be used instead of glassballs. The particles of filter material are preferably large enough soas not to pack tightly, and to leave adequate voids for passage of fuelvapor. At its inner end the tube 100 is formed with openings 105. Thefitting at the outer end of the tube 100 is connected to one end of aline 106, the other end of which is connected to the valve 16 of theintake 42 of the burner 11. The line 106 passes over the burner 11.

In operation the filter of Figure 2 functions as follows: Hot fuel vaporcontaining decomposed lead compounds which have not as yet been filteredout, pass through the line into the annular space 101 between the outertube 97 and the inner tube 100. The body of liquid fuel surrounding theouter tube 97 acts as a coolant, thereby effectiveiy cooling the hotfuel vapor. During the starting period some of the fuel vapor willcondense, but after the interior of the tube 97, including the innertube and its contents, have been brought up to operating temperature, nofurther condensation of consequence occurs. The coolant (i. e., theliquid fuel 18) cools the fuel vapor sufficiently to condense anddeposit thermally decomposed lead compounds, but it does not condensethe hy drocarbon fuel itself except to the limited extent noted.Decomposition of the lead compounds in the vaporizer 13a requires thatthe fuel be heated considerably above the end point of the fuel itself;e. g., such thermal decomposition may require a temperature of 800 F.whereas at 300 F. the gasoline will be completely vaporized.Accordingly, a sufficiently wide temperature rangeabout 500 F. in atypical case-is provided for deposition of lead decomposition productswithout condensation of the hydrocarbon fuel.

The cooled fuel vapor then passes through the openings 105 at the innerend of the tube 100 and then through the tube 100, out through thefitting 103 and into the line 106 where it is reheated by the burner 11.The fuel vapor then passes through the valve 16 and the intake 42 intothe burner 11. It is in the tube 100 that filtration of decomposed leadcompounds takes place.

It will be apparent that the hot fuel vapors containing decomposed leadcompounds are cooled before filtration, and that the cooling medium isthe liquid fuel itself. I have found that there are distinct advantagesin this mode of operation. A more effective filtering action is obtainedby precooling the fuel vapors. Apparently at high temperatures such asprevail in the combined vaporizer and filter 13 shown at Figure 1, it isdiflicult for the decomposed lead compounds to filter out and there issome tendency for these compounds to be carried out of thevaporizer-filter and into the burner, where they are dispersed to theatmosphere. Also, there is a tendency for the decomposed lead compoundsor products of thermal decomposition of the hydrocarbons, to bake ontothe filter medium at the high temperature prevailing in thevaporizer-filter 13. Precooling the hot vapors before filtrationobviates these difficulties.

Such precooling of the fuel vapors can, of course, be accomplished byatmospheric cooling, as by leading the hot vapors through a coil exposedto the atmosphere. However, atmospheric temperature is more variablethan the temperature of the liquid fuel. Also, atmospheric coolingrequires coils or some equivalent structure presenting a heat exchangesurface to the air, and this structure must be external to the burnersystem. Thus extra space is required for atmospheric cooling, and theprovision of extra space may be difficult or impossible. Thus, thedesigner may be required to install the extra system within a smallspace in a cabinet, with no allowance for external coils.

'Yet another advantage of. the cooling system of Figure 2 is as follows:Heat is absorbed by the liquid fuel in tank 12 from the fuel vapor.Should the fuel vapor become excessively hot, it will heat the liquidfuel correspondingly and will raise its pressure. When the pressureexceeds a predetermined value, e. g., 40 pounds per square inch, thevalve 40 will close. Excess pressure will be bled off through the pipe45 and will be burned. This will rapidly relieve the excess pressure, asexplained above.

I have also found that glass balls such as those shown at 104, or otherlike filter medium, provides a more effective filtering medium and/ oris more easily cleaned than conventional filtering media such as steelwool. Thus, from time to time it is sufficient merely to unscrew thefitting 99, remove the inner filter unit, and hold it with the inner enddown to allow drainage of condenser fuel therefrom. The fuel will carrywith it a deposit of filtered lead compounds. This is apparent from thedirty, black color of the liquid flowing out of the holes 105 at the endof the tube 100. A more thorough cleaning and re juvenation can beaccomplished by removing the end fitting 103, pouring out the glassballs 104 and rinsing them with clean gasoline. By way of contrast,steel wool is diflicult or impossible to clean and rejuvenate. It iscommonpractice to discard a steel wool filter when it has become cloggedand fouled. My preferred filter material can be rejuvenated and re-usedindefinitely.

In the systems of Figures 1 and 2, starting can be facilitated byminimizing the surface area of liquid fuel in the fuel tank 12, e. g.,by employing a tank of relatively great vertical length and relativelysmall horizontal diameter. A smaller surface area minimizes condensationof fuel vapor, which is a source of trouble in starting a burner.

Yet another advantage of the systems of my invention, is theminimization or elimination of pulsations. During the operation of aburner in which liquid fuel is vaporized, then supplied to the burner inthe form of vapor, difficulty is encountered, especially during startingby pulsations. These pulsations arise because, as the pressure increasesin the vaporizer, it passes back through the fuel line into the tank.This occurs because of the restricted character of the nozzle or orificeat the outlet end of the fuel line. The restricted character of thisorifice does not permit relief of pressure through the outlet; hencepressure backs up into the fuel tank.

This phenomenon causes pulsation of the flame and may extinguish theflame. It is troublesome during starting when the vapor pressure is low.

In accordance with my invention, hot fuel vapor is supplied to the fueltank to pressurize the fuel supply. It has been proposed heretofore tosupply fuel vapor from the vaporizer to the fuel tank, e. g. in Stein U.S. Patent No. 2,450,025, granted September 28, 1948, entitled GasolineField Stove. However, in such prior design, the vapor is taken off atthe inlet of the vaporizer, and no automatic control means is providedto diminish the fuel supply when the flame becomes too hot.

A connection between the vaporizer inlet and the fuel tank is notadequately effective in evening out pulsations, and it has the furtherdisadvantage that the vapor at the vaporizer outlet is relatively cool,hence condenses more readily in the fuel tank. And when the fuel vaporcondenses it is no longer effective to pressurize the fuel supply. Byconnecting the outlet of the vaporizer to the fuel tank, thesedifficulties are overcome; pulsations are greatly reduced or eliminatedand the fuel supply is effectively pressurized.

The lack of an automatic pressure control in prior systems isdisadvantageous for reasons noted above; when the flame becomesexcessively hot, a greater fuel pressure is communicated to the fuelsupply, and this greater fuel pressure feeds more fuel to the burner,hence makes the flame hotter. This difficulty is obviated in accordancewith the present invention by providing an automatic valve at 40 whichcuts off the supply of liquid fuel to the vaporizer Cir and burner whenthe fuel pressure exceeds a predetermined value.

It will thus be apparent that the burner systems of the presentinvention achieve the several objects set forth hereinabove. They areadapted to operate on a volatile liquid fuel such as gasoline,.tovaporize the fuel and to decompose and filter out lead compounds. Theyare simple to start, require a minimum number of starting operations andthe problem of pulsation is eliminated or greatly diminished.

The starting system shown in Figures 1 to 9 is substantially automaticin its operation. It provides the heat necessary to vaporize thegasoline which is burned during the starting operation, and it alsopressurizes the fuel tank and heats the fuel vaporizer to operatingtemperature.

The entire unit is compact. Also certain important safety features areprovided which are automatic in their operation. Thus the valve 20 issuch that the fuel pressure is not allowed to exceed a predeterminedvalue. Yet the valve 20 operates in a manner to avoid interruption ofthe main burner. If, because of heat from the burner and a high ambienttemperature, the fuel in the tank 12 becomes overly heated, the valve 49operates to automatically shut off the flow of liquid fuel to the mainburner, but the burner is not extinguished.

Among other features, a novel and advantageous filter, and a novel meansfor reheating and rte-evaporating condensed fuel vapor are provided.

I claim:

1. A burner system comprising a fuel tank for volatile liquid fuel, amain burner and a main fuel vaporizer connected to the fuel tank toreceive liquid fuel therefrom and to said main burner to supply fuelvapor thereto; an auxiliary burner connected to receive a combustiblefuel and air mixture for operation thereof from the cornbustible mixturesupplied to said main burner for heating said main fuel vaporizer duringnormal operation of the main burner; a second vaporizer having an inletconnected to the fuel tank to receive liquid fuel therefrom and anoutlet remote from said inlet and connected to said tank to apply thepressure of the vapor generated in said second vaporizer to said tank;said second vaporizer being heated by said auxiliary burner; a starterburner for heating said main fuel vaporizer and said second vaporizerduring starting of the burner system, and a third vaporizer connected tothe fuel tank to receive liquid fuel therefrom, said third vaporizersupplying vaporized fuel to the starter burner.

2. In a burner system of the type comprising a fuel tank, a burner and amain vaporizer, and means including conduit forming meansinterconnecting said elements to supply liquid fuel from the tank to themain vaporizer and to supply fuel vapor from the main vaporizer to theburner; a second vaporizer having an inlet connected to the fuel tank toreceive liquid fuel therefrom and an outlet remote from said inlet andconnected to said tank to supply fuel vapor thereto for pressurizing thetank, means for heating said second vaporizer, a first automatic valveoperable automatically to terminate flow of liquid fuel to said mainvaporizer when the fuel pressure in the fuel tank reaches a firstpredetermined value, a second automatic valve operable automatically toterminate flow of liquid fuel to said second vaporizer when the pressurein the fuel tank reaches a second predetermined value which is less thansaid first value and means including conduit forming means for supplyingvaporized fuel from said tank to said burner during the portion of theperiod of operation of said burner system when said first automaticvalve means is closed.

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